Our understanding of the regulation of bone formation is still incomplete. This is in part due to the complexity of the effects of systemic hormones and growth factors on bone and to our limited knowledge about the regulation of bone formation by local factors. Recent studies from various laboratories, including our own, have indicated the existence of local bone growth factors. Dring the next three years, we plan to complete the isolation, and chemical and biological characterization of bone-derived growth factors (BDGF) from fetal rat calvariae. BDGF will be purified from calvarial conditioned medium by dialysis, gel filtration chromatography, normal and reverse phase liquid chromatography (LC) and, if needed, isoelectric focusing (IEF). The purity and molecular weight of BDGF will be determined by IEF and LC. After the isolation procedure is completed, we will study the cellular source, the regulation of the synthesis, and the effects and mechanisms of action of BDGF on bone formation. For this purpose, we will examine the effects of BDGF on bone DNA and collagen synthesis in cultured fetal rat calvariae using a system developed to study the effects of systemic hormones and growth factors. To confirm an effect on bone formation, we will examine effects on parameters of osteoblastic function, such as the measurement of type I collagen synthesis and alkaline phosphatase activity, and on bone matrix synthesis as determined by bone histomorphometry and autoradiography. We will also study the differential effects of BDGF on periosteum and periosteum-free bone and compare them with effects on osteoblast-like rat osteosarcoma cell lines. The specificity of BDGF for bone will be determined by examining their effects on cartilage and fibroblast cultures. In addition, we will study the interactions of BDGF with systemic hormones and growth factors and compare BDGF with related factors purified by other investigators. An assay for BDGF, using LC or radioimmunoassay, is planned and may have future clinical applications. These investigations should help us understand the role of local bone growth factors in the regulation of bone formation and in the pathogenesis of metabolic bone disease.